Yes it has already been mention. And also, yes it cool.

it's not hard to do at all. took me much longer to download and reinstall half life 2 again. the directions are simple. just don't get your hopes up as much as i did. i seriously think that HL2 + Portal = best game ever.

but this isn't exactly it. remember, the game is not meant to do this. you are actually playing Portal with the HL2 single player maps loaded, so you run into a few problems because things are not exactly working properly.

i kept 'porting into places i wasn't supposed to be and got stuck. also, the enemies can't go through the portals. it's cool for a few minutes, and worth doing if you already have the games. however, just keep hoping Valve releases something like this that is official. we need the real thing. i think if they actually release HL2 Campaign with Portal integrated, i will lose my soul to it.